In many integrated circuit multi-component arrangements, there is often a need to utilize epoxy (or any other appropriate adhesive) to join one component to another during various assembly and/or packaging operations. Indeed, and for the purposes of the present discussion, it will be presumed that the joining relates to attaching a micro-component to a supporting substrate. The need to attach a micro-component to a substrate is a common process step in electronic integrated circuit assemblies, optical system subassemblies, opto-electronic arrangements, and the like.
As the size of these micro-components continues to shrink, the need to place the elements with improved alignment accuracy increases. This is particularly true in optical or opto-electronic arrangements, where one or more micro-components forms part of an optical signal path that requires inter-component alignment to maintain the integrity of the signal path. For example, in a silicon photonic assembly, components such as micro-lenses and optical fibers need to be aligned to one another with sub-100 nm positional accuracy as they are attached to a common substrate, such as a silicon-on-insulator (SOI) substrate.
While the ability to accurately place these micro-components on a substrate is a necessary requirement, the maintenance of these positions over the lifetime of the assembly is also important. It is quite possible that a given assembly will be subjected to variations in temperature, humidity and the like over its lifetime, where these environmental changes may degrade the quality of the adhesive bond and cause one component to shift relative to another. One way to address the lifetime issue is to utilize as thin a bond line as possible in the original attachment process (a “bond line” being defined as the thickness of the adhesive between the two surfaces being bonded). It has been found that bond lines on the order of tens of microns will increase the lifetime stability of micro-component assemblies. However, this relatively thin bond line has presented problems in terms of the friction-based restriction of the flow of the adhesive (i.e., molecular flow regime), associated with the relatively large surface areas to be joined relative to the total volume (relatively small) of the adhesive. This frictional problem associated with the small amount of adhesive material then also limits the amount of post-placement adjustment of the micro-component that may be performed, eliminating the possibility of performing active or quasi-active alignment in many optical or opto-electronic systems.
Arrangements exist in the prior art for addressing various issues related to joining components using an epoxy or other adhesive. US Patent Publication 2009/0115039 issued to Z. Zhu et al. on May 7, 2009 is associated with controlling the bond line thickness of the epoxy used in semiconductor device attachments. The Zhu et al. arrangement, however, is concerned with creating relatively “thick” bond lines (as opposed to the “thin” lines desired in the present circumstances) and uses boundary walls around the perimeter of a bonding area to serve as a dam to prevent the epoxy from flowing into unwanted areas.
Many other references exist in the art related to preventing the flow of epoxy into unwanted areas, forming ‘wick-stop’ trenches and the like. U.S. Pat. No. 6,526,204 issued to D. W. Sherrer et al. on Feb. 25, 2003 is exemplary of this technology, where a trench is formed in a direction “away” from an optical signal path/fiber supporting groove. Thus, any overflow amounts of epoxy will be directed out of the signal path and into wick-stop trench.
These trenches, however, are of limited use in situations where there are multiple components that need to be placed in close proximity. That is, there are many system arrangements where the inclusion of one or more wick-stop trenches requires too much valuable surface area in the arrangement.
A need therefore remains for an arrangement for better controlling the application and control of an adhesive used to join a micro-component to a substrate.